Method and apparatus for the slow drying of stored material



F. W. LAUCK Aug. 30, 1955 METHOD AND APPARATUS FOR THE SLOW DRYING OF STORED MATERIAL Filed July 19, 1952 AT TORNEYS United States Patent 6 METHOD AND APPARATUS FOR THE SLOW DRYING F STORED MATERIAL Francis W. Lauck, Milwaukee, Wis., assignor to A. O. Smith Corporation, Milwaukee, Wis., a corporation of New York Application July 19, 1952, Serial No. 299,865

9 Claims. 01. 34-27 This invention relates to the dehumidification of gases and more particularly to a method and apparatus for the dehumidification of a fluid employed in a system for slow drying of stored grain.

An object of the present invention is to provide a system for removing moisture from stored material by passing fluid which is at approximately atmospheric temperature through the material and thereafter condensing the water from the fluid in preparation for recycling.

Another object of the invention is to provide a simple and effective method of drying a moist fluid without the use of an external coolant, whereby a portion of the moist fluid is compressed and the uncompressed portion of the fluid is employed to cool the compressed fluid and condensed Water therefrom.

Still another object is to provide a method of dehumidifying fluid to be used for drying stored material which does not require an outside source of heat.

Another object is to provide a lightweight unit for dehumidifying and recirculating a fluid into stored grain which may be conveniently moved and adapted for use at various storage locations.

Still another object is to provide an inexpensive dehumidification unit for farm use which has a small operational cost.

The present invention is directed to a dehumidification unit for drying air or gas which is circulated by an air compressor or other means such asa fan in a closed system through stored material contained in a substantially airtight container or vessel to remove moisture from the material and slow dry the same.

The air having circulated through the stored material passes from the container through a suitable conduit to the dehumidification unit where a portion of the air is drawn into a compressor. The remaining portion of the air is by-passed around the compressor and passes directly through the dehumidification unit to an outlet opening therein.

The portion of the air drawn into the compressor is compressed to a pressure of about 20 pounds per square inch or greater and the temperature of the compressed air is thereby increased.

The compressed air then enters a heat exchanger wherein the compressed air is cooled by the uncompressed air which has by-passed the compressor and is directed over the heat exchanger. Cooling the compressed air causes moisture to condense from the same, and this moisture is removed from the air by a suitable means such as a bafile chamber.

The dehumidified air is then allowed to expand through a venturi tube, disposed adjacent the outlet in the unit, into the flow path of the uncompressed air. This expansion acts as a jet and serves to move the air through the unit and hence through a discharge conduit into the storage container. The dried air passes through the bed of stored material and absorbs moisture from the'material to' dry the same.

Other objects and advantages of the invention will appear hereinafter in connection with the description of the accompanying drawing.

In the drawing:

Figure 1 is an elevational view with parts broken away and sectioned and showing the dehumidification unit as employed in conjunction with a silo; and

Fig. 2 is a vertical section of the dehumidification unit.

Referring to the drawing, there is shown an air de-' humidification unit 1 as applied to a closed system which comprises, in general, a storage tank or silo 2 containing the stored material 3 to be dried, an air discharge conduit 4 to conduct dried air from the dehumidification unit 1 to the bottom portion of silo 2, and an air return conduit 5 to conduct moist air from the top of the silo 2 to unit 1.

Silo 2 may be any concrete or steel structuresu'ch as is ordinarily used to store grain, silage or the like. If a closed or recycling system of air drying is to be employed to dry the material 3 it is necessary that the silo 2 be of a closed construction and as airtight as practical so that the drying air may circulate through the system without undue leakage to the atmosphere.

Dehumidification unit 1 comprises, in general, a hollow external casing 6, an air compressor unit 7 mounted within casing 6 and a heat exchanger 8' also mounted within casing 6 and communicating with compressor unit 7.

One end of casing 6 is provided with an inlet opening 9 which receives a flanged fitting 10 to which return conduit 5 is attached. The opposite end of the casing is provided with an outlet opening 11 which receives the discharge conduit 4.

Air compressor 7 is shown as mounted within casing 6 in the vicinity of the inlet opening 9 and is provided with a funnel-like inlet pipe 12. Pipe 12 is provided with a butterfly valve 13 or the like to control the amount of moist air admitted tocompressor 7. A suitable small capacity motor 14 is disposed within casing 6 and is employed to drive compressor 7. The air compressor may also be located outside the casing as well as the motor that drives the same.

In operation, the moist air at approximately atmospheric temperature is drawn from silo 2 by compressor 7 through conduit 5 to the dehumidification unit 1. A portion of the air entering casing 6 is admitted to air compressor 7 by valve 12 While the remaining air passes on through casing 6. The amount of air to be drawn into compressor 7 is dependent on the capacity of the cornpressor, the temperature of the air, the rate of drying desired, and other factors. With the use of a small capacity compressor as might be available on a farm,- it may be desirable to admit about one-third to one-half of the entering air to the compressor with the remaining portion passing directly through casing 6 and serving to subsequently cool the compressed air.

The portion of the air admitted to the compressor 7 is compressed to a pressure of about 20 pounds per square inch or greater and the temperature of the air as it is compressed is substantially increased.

The compressed air leaves compressor 7 at the upper end through conduit 15" and passes therethrou'gh to heat exchanger 8. As shown, heat exchanger 8 comprises an inlet header 16 which receives the compressed air from conduit 15, an outlet header 17 from which the cooled air is discharged and a plurality of vertical tubes 1 3 which connect headers 16 and 17 and serve as the heat transfer surface. The cool air by-passing compressor 7 in casing 6 passes across tubes 18 and acquires heat from the warmer compressed air within the tubes. plates 19 and 20 may be employed as shown in Fig. 2 to direct the by-passed or uncompressed air over the tubes 18. As the uncompressed air passes over tubes 18 and heat is transferred from the compressed air within the tubes to the uncompressed air, the temperature of the compressed air is lowered below its dew point and water is condensed from the compressed air.

As substantially all of the water condensed in heat exchanger 8 is apt to be entrained with the air in the'form of a mist or spray, a suitable separating apparatus is employed. This apparatus may take the form of a baflie chamber 21. The cooled air carrying the entrained Water is conducted from heat exchanger 8 through pipe 22 to chamber 21 wherein the air strikes a bafiie plate 23. This striking action causes a separation of air and water and the water precipitates downwardly through a suitable opening in chamber 21 to sump tank 24, wherein the water is collected. A suitable tap 25 is employed to drain the water from tank 24 when desired.

To insure removal of any non-entrained condensate from heat exchanger 8, the bottom surface of outlet header 17 may be inclined so that the condensate will flow by gravity from header 17 through pipe 22 and chamber 21 to tank 24.

The air or gas, substantially free from entrained water, leaves chamber 21 through nozzle 26 and expands therefrom into discharge conduit 4 and into the flow path of the uncompressed or by-passed portion of the air. Conduit 4 takes the form of a Venturi tube or other restricted cross-sectional member so that the expansion of the compressed air from nozzle 26 into conduit 4 acts as a jet or aspirator and serves as a prime mover for the system by drawing the uncompressed or by-passed air through the unit 1.

The expansion of the air as it leaves nozzle 26 cools the air to approximately atmospheric temperature so that the air discharged from conduit 4 is at approximately the same temperature as the air entering unit 1 through conduit 5. However, it is possible that the air discharged from unit 1 may be slightly warmer than the air entering the unit for the uncompressed portion of the air acquires some sensible heat from compressor 7 and there is a little heat loss to the atmosphere in the unit.

The air having lost considerable moisture in unit 1 is discharged from conduit 4 into the bottom of silo 2 and passes upwardly through the bed of stored material 3 absorbing moisture from the material during the passage. The saturated air at the top of silo 2 is then recycled downwardly by operation of compressor 7 through conduit and hence to the dehumidification unit 1.

The dehumidification system of the present invention may be employed to dehumidify any moist fluid such as gas or air and is particularly adaptable to farm usage or other operations where rapid drying is not required. An effective dehumidification can be accomplished with a minimum of equipment without supplying heat by circulating the air through the system at its normal temperature which will approximate atmospheric temperature in most instances. Thus, if the air being discharged into the stored grain is at a temperature near or slightly above the atmospheric or grain temperature a more eflicient drying can be obtained per mass of air passing through the grain, and no external source of heat is necessary. However, the drying time will be appreciably longer when using air at atmospheric temperature than the drying time if heated air is discharged into the grain. This invention enables the farmer to eflectively dry the stored material with the use of only a small motor and small capacity compressor without the need for an outside heating source or an external coolant and pumping system for the coolant.

Another advantage of the invention is that the temperature of the drying fluid does not have to be controlled as the invention will operate over a wide range of temperatures. Fluctuations in air temperatures due, for example, to heating in the daytime and cooling at night, are permissible. Seasonal temperature fluctuations may cause the efliciency of the unit to vary but this is merely a matter of running the unit for a shorter or longer period of time.

Various embodiments of the invention may be employed within the scope of the accompanying claims.

I claim:

1. A system and apparatus for removing moisture absorbed by a fluid following circulation of the fluid through grain or the like stored in a sealed storage structure and prior to recirculation of the fluid through said grain which comprises a housing, conduit means connecting the storage structure to the inlet and discharge of said housing, a compressor disposed in said housing, a heat exchanger disposed adjacent the compressor within said housing, a conduit connecting the compressor and heat exchanger, means to drive said compressor to establish circulation of the fluid through the structure, housing and conduit means, baflie means in said housing to direct a portion of the circulated fluid through said compressor and connecting conduit and heat exchanger and direct another portion of the gas over said heat exchanger, the fluid passing through the compressor being compressed substantially therein and lowered in temperature in said heat exchanger below the dew point to condense the moisture therefrom absorbed by contact with the stored grain prior to recirculation of the fluid through the grain, means to separate the water of condensation from the compressed portion of the fluid, and restricted cross-sectional means communicating with said heat exchanger for expanding the compressed portion of said fluid into the flow path of the uncompressed portion of said fluid to move said uncompressed portion through the housing and discharge the same with the dehumidified fluid into said storage structure.

2. A system and apparatus for removing moisture absorbed by a fluid following circulation of the fluid through grain or the like stored in a sealed storage structure and prior to recirculation of the fluid through said grain, which comprises a housing having an inlet and an outlet therein, conduit means connecting the storage structure to the inlet and outlet of said housing, a compressor disposed in said housing, a heat exchanger disposed adjacent the compressor Within said housing, a conduit connecting the compressor and heat exchanger, means to drive the compressor to establish circulation of the fluid through the structure, housing and conduit means, bafile means in said housing to direct a portion of the circulated fluid through said compressor and connecting conduit and heat exchanger and direct another portion of the fluid over said heat exchanger and to the outlet, the fluid passing through the compressor being compressed substantially therein and lowered in temperature in said heat exchanger below the dew point to condense the moisture therefrom absorbed by contact with the stored grain prior to recirculation of the fluid through the grain, means to separate the condensed moisture from the compressed portion of the fluid, and

i a venturi connected to said heat exchanger and discharging the dehumidified fluid into the outlet conduit in the flow path of the uncompressed fluid to effect movement of the uncompressed fluid through the housing and across the heat exchanger and discharge of the same with the dehumidified fluid into said storage structure.

3. A closed system for drying stored material contained in a substantially airtight container, which comprises a hollow casing having an inlet opening for receiving moist fluid and an outlet opening for discharging ing, the remaining portion of said moist fluid passing around said compression means to said outlet opening,

heat transfer means disposed within said casing and communicating with sm'd compression means and defining a passageway for the compressed portion of said fluid, said heat transfer means serving to transfer heat from the compressed portion of said fluid to the uncompressed portion of said fluid with the temperature of the compressed portion of said fluid being lowered below the dew point thereof to condense water from said compressed portion, means for separating the condensed water from the compressed portion of the fluid, and restricted cross-sectional means communicating with said heat transfer means for expanding the compressed portion of said fluid into the flow path of the uncompressed portion of said fluid to move said uncompressed portion through the casing into said fluid discharge means.

4. An assembly for dehumidifying a fluid made moist by absorption of moisture from forage material stored in a sealed container, which comprises a hollow casing having an inlet opening therein for receiving moist fluid from said container and an outlet opening therein for discharging dried fluid into said container, compression means disposed within said casing for compressing a portion of the moist fluid entering said casing, the remaining portion of said moist fluid passing around said compression means to said outlet opening, heat transfer means disposed within said casing and communicating with said compression means and defining a passageway for the compressed portion of said fluid, said heat transfer means serving to transfer heat from the compressed portion of said fluid to the uncompressed portion of said fluid with the temperature of the compressed portion of the fluid being lowered below the dew point thereof to condense water from said compressed portion, means to separate the water of condensation from said fluid, and restricted cross-sectional means communicating with said heat transfer means for expanding the compressed portion of said fluid into the flow path of the uncompressed portion of said fluid to move said uncompressed portion through the casing.

5. A closed cycle method of drying stored material contained in a substantially airtight vessel, which comprises introducing substantially dry fluid into one end of said vessel, withdrawing moist fluid from the other end of said vessel, said fluid flowing through the stored material and acquiring moisture from said material dur ing the flow, introducing a portion of the moist fluid into a fluid compression means to compress the same, by-passing the remaining portion of the moist fluid around said compression means, utilizing the by-passed portion of said fluid to cool the compressed portion of the fluid with water being condensed from the compressed fluid as the same is cooled below the dew point thereof, separating the condensed water from the compressed portion of the fluid, expanding the compressed portion of the fluid into the flow path of the by-passed fluid, and recycling the dried fluid through the stored material in said vessel.

6. A method of dehumidifying moist fluid, which comprises introducing a portion of the moist fluid into a fluid compression means to compress the same, bypassing the remaining portion of the moist fluid around said compression means, utilizing the by-passed portion of said fluid to cool the compressed portion of the fluid with water being condensed from the compressed fluid as the same is cooled below the dew point thereof, and separating the condensed water from the compressed portion of the fluid.

7. A method of dehumidifying moist fluid, comprising introducing the fluid into a hollow casing, cornpressing a portion of the fluid within said casing, utilizing the remaining uncompressed portion of said fluid to cool the compressed portion of the fluid, the temperature of the compressed fluid being lowered below the dew point thereof to condense water from said compressed fluid, separating the condensed water from the compressed fluid, and expanding the compressed fluid through a restricted cross-sectional opening into the flow path of the uncompressed fluid to recombine the compressed fluid and the uncompressed fluid and move the same through said casing.

8. A method of dehumidifying moist fluid comprising introducing a portion of a collection of moist fluid into a fluid compression means to compress the same, introducing the compressed portion of said fluid into a heat exchanging means, passing the uncompressed portion of said fluid over said heat exchanging means to cool the compressed portion of the fluid with water being condensed from the compressed fluid as the same is cooled below the dew point thereof, separating the condensed water from the compressed fluid, and expanding the compressed portion of the fluid into the flow path of the uncompressed portion of the fluid to recombine the fluids.

9. An apparatus for dehumidifying a gas containing a substantial amount of Water vapor, which comprises a gas compressor, heat transfer means communicating with said compressor and defining a passageway for the compressed gas, means to introduce a portion of said gas to said compressor, means to by-pass a second portion of said gas around the compressor and directing the same across the heat transfer means to transfer heat from the compressed portion of the gas to said second portion of the gas with the temperature of the compressed portion of the gas being lowered below the dew point thereof to condense water from said compressed portion, means to separate the water of condensation from the compressed portion of said gas, and a restricted cross-sectional member communicating with said heat transfer means for expanding the compressed portion of said gas into the flow path of the second portion of said gas to move said gas through the apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 173,198 Winants Feb. 8, 1876 912,873 McCall Feb. 16, 1909 1,620,289 Ridley Mar. 8, 1927 1,982,622 Anger Dec. 4, 1934 2,119,201 Cook et al. May 31, 1938 2,564,475 Fischer Aug. 14, 1951 2,586,002 Carson Feb. 19, 1952 2,628,482 Burgess Feb. 17, 1953 2,680,599 Wile June 8, 1954 FOREIGN PATENTS 229,249 Switzerland Jan. 17, 1944 

